Atrial fibrillation can be treated by isolating portions of the atria. Such isolation of the atria can be done by open-heart surgery (e.g., a modified Maze procedure) or, most commonly, by a trans-venous catheter technique. In the majority of cases, the doctor cauterizes the left atrial muscle tissues using radiofrequency ablation techniques, with the ablation lesion targeting and/or circumscribing the pulmonary veins. Isolation of these anatomic portions of atria prevents the electrical propagation of the arrhythmia into the remainder of the atria. The operator places electrophysiologic catheters into the right heart. Under fluoroscopic guidance, a catheter is advanced adjacent to the atrial septum. In most cases, a puncture of the atrial septum (right to left) is made with a specialized needle catheter. A guide-wire is then advanced into the left atrium.
The trans-septal catheter is removed and a guide catheter is delivered over the wire into the left atrium. An ablation catheter is then advanced into the left atrium under fluoroscopic guidance. Typically, electrophysiologists use additional imaging and mapping technology to improve safety and efficacy of the procedure, such as intercardiac ultrasound, cardiac CT, or non-contact mapping systems. Once the ablation/mapping catheters are in the left atrium, the operator delivers radiofrequency energy to the target sites. The operator moves the ablation catheter in a point-by-point fashion connecting the lesions to effectively electrically isolate the pulmonary veins from the rest of the atrium.
These known procedures typically take 3-6 hours to complete. The procedural success varies between operators and patient selection (success rate is between 50-85% for a single attempt). A substantial minority of patients requires subsequent ablation procedures to “touch up” the prior ablation site. The cost of these procedures is highly variable and increases substantially with duration of procedure and the addition of adjuvant imaging/mapping technology. The current procedures are associated with a 5.6% risk of procedural complications, including a 1/200 risk of stroke due to the need to instrument (i.e., place one or more medical devices into) the left atrium. Other concerning complications include cardiac perforation, tamponade, pulmonary vein stenosis, and atrial-esophageal fistula. Despite attempts to simplify and streamline the procedure, the anatomic variations of the left atrium and pulmonary veins have limited the utility of alternative ablation techniques.
Known epicardial techniques for atrial fibrillation also have various limitations. For example, most current epicardial ablation strategies require the operator to blindly navigate recesses of the pericardial space with an ablation catheter, and reflections of the pericardial anatomy pose an obstacle to delivery of a single contiguous lesion 30 using these techniques. (See the broken line in FIG. 1.) Thus, the pericardial anatomy greatly limits the efficacy and technical ease of current pericardial/epicardial catheter-based procedures.
Although the membranous reflections of the pericardial space that must be breached are very thin and relatively avascular, the angle, spatial limitations, and relative orientation of the surgical access point to the adjacent pericardial reflections do not facilitate simple puncture with a blunt catheter or a standard needle. Moreover, the large vessel and cardiac chambers adjacent to the pericardial reflections make the proposition of blind puncture with conventional catheters very risky.
Currently known cardiac ablation catheters typically require frequent repositioning and/or advanced noncontact mapping techniques to identify incomplete segments in the ablation lesion. For epicardial techniques performed from the pericardial space, such manipulation is fraught with danger and technical limitations. Standard unipolar applications require an externalized grounding pad that results in a diffuse or spherical virtual electrode. Current bipolar ablation techniques utilize electrode pairs that are in close proximity, require the use of cumbersome equipment, and often require entry into both the pericardium and the left atrial blood pool.
Accordingly, there is a need in the pertinent art for devices, systems, and methods for efficiently and reliably locating and puncturing pericardial reflections. There is a further need in the pertinent art for devices, systems, and methods for delivering a single contiguous lesion within the pericardial space without the need for repositioning of equipment.